Freeze-In Dark Matter with Displaced Signatures at Colliders

Raymond T. Co; Francesco D'Eramo; Lawrence J. Hall; Duccio Pappadopulo

doi:10.1088/1475-7516/2015/12/024

paper

Freeze-In Dark Matter with Displaced Signatures at Colliders

arXiv:1506.07532 · doi:10.1088/1475-7516/2015/12/024

Abstract

Dark matter, $X$ , may be generated by new physics at the TeV scale during an early matter-dominated (MD) era that ends at temperature $T_{R} ≪ TeV$ . Compared to the conventional radiation-dominated (RD) results, yields from both Freeze-Out and Freeze-In processes are greatly suppressed by dilution from entropy production, making Freeze-Out less plausible while allowing successful Freeze-In with a much larger coupling strength. Freeze-In is typically dominated by the decay of a particle $B$ of the thermal bath, $B \to X$ . For a large fraction of the relevant cosmological parameter space, the decay rate required to produce the observed dark matter abundance leads to displaced signals at LHC and future colliders, for any $m_{X}$ in the range $keV < m_{X} < m_{B}$ and for values of $m_{B}$ accessible to these colliders. This result applies whether the early MD era arises after conventional inflation, when $T_{R}$ is the usual reheat temperature, or is a generic MD era with an alternative origin. In the former case, if $m_{X}$ is sufficiently large to be measured from kinematics, the reheat temperature $T_{R}$ can be extracted. Our result is independent of the particular particle physics implementation of $B \to X$ , and can occur via any operator of dimension less than 8 (4) for a post-inflation (general MD) cosmology. An interesting example is provided by DFS axion theories with TeV-scale supersymmetry and axino dark matter of mass GeV to TeV, which is typically overproduced in a conventional RD cosmology. If $B$ is the higgsino, $h ~$ , Higgs, W and Z particles appear at the displaced decays, $h ~ \to h a ~, Z a ~$ and $h ~^{\pm} \to W^{\pm} a ~$ . The scale of axion physics, $f$ , is predicted to be in the range $(3 \times 1 0^{8} - 1 0^{12})$ GeV and, over much of this range, can be extracted from the decay length.

26 pages + appendices, 13 figures; v2, JCAP version

Freeze-In Dark Matter with Displaced Signatures at Colliders

Abstract

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